Squamous cell carcinoma of the head and neck (SCCHN), including that of the oral cavity, has a significant level of mortality and a high rate of recurrence. A significant portion of these clinical failures result from tumor cell radiation resistance (RR). Thus, the development of an effective method for sensitizing head and neck tumors to radiotherapy would have a profound effect on the treatment of this disease. Wild-type (wt) p53 plays a crucial role in apoptotic pathways leading to tumor cell death. The lack of functional p53 in many SCCHN tumor cells is thought to be responsible for their RR. The restoration of wtp53 function may restore the p53-mediated apoptotic pathway resulting in more efficient treatment. A combination of wtp53 gene therapy and radiation will be used to restore radiation sensitivity to RR SCCHN. A long-standing goal in gene therapy for cancer is a systemic delivery system that selectively targets tumor cells, including metastases. This application proposes to optimize a folate-linked liposome systemic delivery system for wtp53 to improve the efficacy of conventional radiotherapy. Preliminary in vivo results have proved in principle that restoration of wtp53 function enhances radiation induced apoptosis, leading to long term total tumor regression. In collaboration with a pharmaceutical partner, we will obtain GMP grade reagent, perform toxicology and pharmacokinetic studies to obtain IRB, IBC and FDA approval. Once approvals are obtained we will use this combination therapy in a Phase I clinical trial in an effort to translate this new and potentially more effective treatment modality into the clinic for head and neck cancer.